Modern aircraft generally have a first synthetic vision system, called “SVS”. This system makes it possible to present the crew with a synthetic image of the outside landscape generally comprising piloting or navigation information. An SVS system comprises a mapping database representative of the terrain being flown over, a geolocation system and electronic computation means. The image displayed is a three-dimensional view of the outside represented as realistically as possible.
These aircraft also have a second display system called “EVS”, the acronym for “Enhanced Vision System”. This second system comprises one or more sensors which can be optical sensors in the visible or infrared range or intensified imaging, or lidars or even radars. The image is generally processed.
The combined image obtained from the SVS and EVS images is called CVS. It is displayed on the display screens which are located on the front face of the instrument panel of the aircraft. The point of view displayed is in the axis of the aircraft.
The CVS image is an interesting solution for operations called “EVO”, the acronym for “Equivalent Visual Operations”, for aircraft operating in flight by instruments, a flight called “IFR” for “Instrument Flight Rules”, or even to improve the safety of flights of aircraft operating in flight with degraded view, flights called “VFR” with a degraded visual environment, VFR being the acronym for “Visual Flight Rules”. The SVS image enhances the awareness of the situation with regard to the far terrain whereas the EVS image does so for the near terrain, rendering the combination of the two images particularly relevant.
The superimposing of the SVS and EVS images is not necessarily simple. One possible solution consists in superimposing all of the EVS image on the SVS, thus masking a useful part of the SVS, possibly with a realignment of the SVS on the EVS by identification of a notable element such as a landing runway, which limits the cases of use to, for example, landing on a runway. A second solution is to display the EVS image only under the horizon and to display the SVS image only above the horizon. This all-or nothing solution does not always exploit all the potential of the two images. A third solution consists in detecting the zones with a contrast higher than a threshold in the EVS image and superimposing only these zones on the SVS image. Here again, the risk of losses of useful information is not negligible.